U.S. patent application number 13/613640 was filed with the patent office on 2014-03-13 for elevator rope sway and disturbance estimation.
The applicant listed for this patent is Mouhacine Benosman. Invention is credited to Mouhacine Benosman.
Application Number | 20140069747 13/613640 |
Document ID | / |
Family ID | 49170775 |
Filed Date | 2014-03-13 |
United States Patent
Application |
20140069747 |
Kind Code |
A1 |
Benosman; Mouhacine |
March 13, 2014 |
Elevator Rope Sway and Disturbance Estimation
Abstract
A sway of an elevator rope is determined during an operation of
an elevator system. A disturbance of the elevator system is
determined based on a state model of the elevator system and at
least one measurement of a state of the elevator system. The sway
of the elevator rope is determined based on the disturbance and a
system model of the elevator system.
Inventors: |
Benosman; Mouhacine;
(Boston, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Benosman; Mouhacine |
Boston |
MA |
US |
|
|
Family ID: |
49170775 |
Appl. No.: |
13/613640 |
Filed: |
September 13, 2012 |
Current U.S.
Class: |
187/414 |
Current CPC
Class: |
B66B 7/06 20130101 |
Class at
Publication: |
187/414 |
International
Class: |
B66B 5/02 20060101
B66B005/02 |
Claims
1. A method for determining a sway of an elevator rope during an
operation of an elevator system, comprising: determining a
disturbance of the elevator system based on a state model of the
elevator system and at least one measurement of a state of the
elevator system; and determining the sway of the elevator rope
based on the disturbance and a system model of the elevator system,
wherein steps of the method are performed by a processor.
2. The method of claim 1, wherein the at least one measurement
includes a measurement of the sway of the elevator rope.
3. The method of claim 1, wherein the sway of the elevator rope
includes a sway function of amplitudes of the sway along a length
of the elevator rope over time, further comprising: adjusting the
sway function based on the measurement.
4. The method of claim 3, wherein the adjusting comprising:
shifting the sway function based on a difference between the
measurement and estimated sway at a time and a location of the
measurement.
5. The method of claim 1, wherein the state model includes a model
of the disturbance, and further comprising: correlating a number of
measurements with a number of unknown coefficients in the model of
the disturbance; measuring the number of measurements; and
determining the unknown coefficients of the disturbance by solving
a system of equations derived from the state model.
6. The method of claim 1, wherein the state model includes a model
of disturbance, and wherein the model of disturbance include a
combination of one or multiple sinusoidal functions with unknown
coefficients.
7. The method of claim 1, wherein the state model is based on an
inverse of the system model.
8. The method of claim 5, further comprising: determining the
number of measurement using a set of sway sensors.
9. The method of claim 8, wherein a number of sway sensors in the
set is less than the number of the unknown coefficients in the
model of the disturbance.
10. The method of claim 9, wherein the sway sensors are arranged at
sway locations, further comprising: adjusting the sway function
based on measurements of the sway sensors at the sway
locations.
11. A method for determining a sway of an elevator rope during an
operation of an elevator system, wherein the sway of the elevator
rope includes a sway function of amplitudes of the sway along a
length of the elevator rope over time, comprising: determining a
disturbance of the elevator system based on a state model of the
elevator system and a number of measurements of a state of the
elevator system, wherein the number of measurements equals a number
of unknown coefficients in the model of the disturbance; and
determining the sway of the elevator rope based on the disturbance
and a system model of the elevator system, wherein the state model
relates the unknown coefficients of the disturbance to the
amplitudes of the sway, and wherein the system model relates an
amplitude of the disturbance to the amplitude of the sway, wherein
steps of the method are performed by a processor.
12. The method of claim 11, further comprising: determining the
number of measurements with a number of sensors, wherein the number
of sensors is less than the number of measurements; and adjusting
the sway based on a difference between the measurement and
estimated sway at a time instance and a location of the
measurement.
13. An elevator system, comprising: an elevator car; an elevator
rope attached to the elevator car; a set of sensors arranged for
determining at a set of measurements of a state of the elevator
system; and a sway measurement unit for determining a sway of the
elevator rope based on the set of measurements, wherein the sway
measurement unit comprises: a memory for storing a state model of
the elevator system and a system model of the elevator system,
wherein the state model relates coefficients of disturbance of the
elevator system to the set of measurements, and wherein the system
model relates an amplitude of the disturbance to the amplitude of
sway of the elevator rope; and a processor for determining the
disturbance of the elevator system based on the state model and the
set of measurements, and for determining the sway of the elevator
rope based on the disturbance and the system model.
14. The system of claim 13, wherein the processor further adjusts
the sway based on a difference between the measurement and
estimated sway at a time instance and a location of the
measurement.
15. The system of claim 13, wherein the set of sensors includes a
set of sway sensors for measuring sways of the rope at a set of
sway locations.
16. The system of claim 15, wherein at least one sway sensor
provides multiple measurements determined in different instants of
time to form the set of measurements of the state of the elevator
system.
Description
FIELD OF THE INVENTION
[0001] This invention relates generally to elevator systems, and
more particularly to measuring a lateral sway of an elevator rope
of an elevator system.
BACKGROUND OF THE INVENTION
[0002] Typical elevator systems include a car and a counterweight
confined to travel along guiderails in, e.g., a vertically
extending elevator shaft. The car and the counterweight are
connected to each other by hoist ropes. The hoist ropes are wrapped
around a sheave located in a machine room at the top (or bottom) of
a building or structure. In conventional elevator systems, the
sheave is powered by an electrical motor. In other elevator
systems, the sheave is unpowered, and the drive means is a linear
motor mounted on the counterweight.
[0003] Rope sway refers to oscillation of an elevator ropes, e.g.,
the hoist and/or compensation ropes. The elevator rope can be any
type of rope suitable for use in the elevator system, such as
cable, chain, or hawser. The oscillation can be a significant
problem in a roped elevator system. The oscillation can be caused,
for example, by vibration emanating from wind induced building
deflection and/or the vibration of the ropes during operation of
the elevator system. If the frequency of the vibrations approaches
or enters a natural harmonic of the ropes, then the oscillation
displacements can increase far greater than the displacements. In
such situations, the ropes can tangle with other equipment in the
elevator system, or as the elevator travels, come out of the
grooves of the sheaves. If the elevator system use multiple ropes
and the ropes oscillate out of phase with one another, then the
ropes can become tangled with each other and the elevator system
may be damaged.
[0004] Several conventional solutions use mechanical devices
connected to the ropes to estimate the displacement of the ropes.
For example, one solution uses a device attached to a compensating
rope sheave assembly in an elevator system to detect rope sway
exceeding a certain magnitude. However, a mechanical device
attached to a compensating rope is difficult to install and
maintain.
[0005] Another method uses displacement and the natural frequency
of the building for estimating and computing the amount of sway of
the rope. This method is general and may not provide precise
estimation of the rope sway.
[0006] Accordingly, there is a need to improve an estimation of a
rope sway methods suitable for the estimation of the rope sway in
real time.
SUMMARY OF THE INVENTION
[0007] Embodiments of the invention are based on a realization that
rope sway can be determined based on a model of an elevator system
when the disturbance of the elevator system is known.
Unfortunately, the disturbance is generally unknown due to, e.g.
cost involved in measurement the disturbance. However, some
embodiments are based on another realization that a state model of
the elevator system can be determined to relate the disturbance of
the system, or a model of the disturbance, to a state of the
elevator system. Thus, based on the state model and a set of
measurements of the state of the elevator system, the disturbance
of the elevator system can be determined. Such realizations allow
for efficient model-based determination of the disturbance of the
elevator system and, subsequently, the sway of the elevator rope,
which is suitable for real-time applications.
[0008] The measurements of the state of the elevator system can be
determined during an operation of the elevator system. The state
can be determined based on various types of measurements, e.g.,
based on measurements of a sway of the rope at sway locations,
measurements of tension of the rope, or measurements of vibration
of the elevator car.
[0009] Some embodiments are based on another realization that if
the state of the system is determined using the measurement of the
sway of the rope provided by the sway sensors, the measurements of
the same sensors can be used to adjust a sway function and to
increase the accuracy of the sway determination.
[0010] Some embodiments are based on another realization that a
number of measurements of the state can be correlated with a number
of unknown coefficients in the model of the disturbance. Also, some
embodiments are based on another realization that a number of
sensors required to determine sufficient number of measurements can
be reduced by using the measurements of the same sway sensor at
different instants of time.
[0011] Accordingly, one embodiment of the invention discloses a
method for determining a sway of an elevator rope during an
operation of an elevator system. The method includes determining a
disturbance of the elevator system based on a state model of the
elevator system and at least one measurement of a state of the
elevator system; and determining the sway of the elevator rope
based on the disturbance and a system model of the elevator system.
Steps of the method are performed by a processor.
[0012] Another embodiment discloses a method for determining a sway
of an elevator rope during an operation of an elevator system,
wherein the sway of the elevator rope includes a sway function of
amplitudes of the sway along a length of the elevator rope over
time. The method includes determining a disturbance of the elevator
system based on a state model of the elevator system and a number
of measurements of a state of the elevator system, wherein the
number of measurements equals a number of unknown coefficients in
the model of the disturbance; and determining the sway of the
elevator rope based on the disturbance and a system model of the
elevator system, wherein the state model relates the unknown
coefficients of the disturbance to the amplitudes of the sway, and
wherein the system model relates an amplitude of the disturbance to
the amplitude of the sway.
[0013] The method can also optionally include determining the
number of measurements with a number of sensors, wherein the number
of sensors is less than the number of measurements; and adjusting
the sway based on a difference between the measurement and
estimated sway at a time instance and a location of the
measurement.
[0014] Another embodiment discloses an elevator system including an
elevator car; an elevator rope attached to the elevator car; a set
of sensors arranged for determining at a set of measurements of a
state of the elevator system; and a sway measurement unit for
determining a sway of the elevator rope based on the set of
measurements. The sway measurement unit includes a memory for
storing a state model of the elevator system and a system model of
the elevator system, wherein the state model relates coefficients
of disturbance of the elevator system to the set of measurements,
and wherein the system model relates an amplitude of the
disturbance to the amplitude of sway of the elevator rope; and a
processor for determining the disturbance of the elevator system
based on the state model and the set of measurements, and for
determining the sway of the elevator rope based on the disturbance
and the system model.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is an isometric schematic of an example elevator
system in which the embodiments of the invention operate;
[0016] FIG. 2 is a side view schematic of a model of the elevator
system according an embodiment of an invention;
[0017] FIG. 3A is a block diagram of a method for determining a
sway of an elevator rope during an operation of an elevator system
according an embodiment of an invention;
[0018] FIG. 3B is a block diagram of a method for adjusting the
sway function based on the measurement according an embodiment of
an invention;
[0019] FIG. 4A is a schematic of a horizontal placement of four
sway sensors within the elevator shaft according an embodiment of
an invention;
[0020] FIG. 4B is a schematic of a horizontal placement of three
sway sensors within the elevator shaft according an embodiment of
an invention;
[0021] FIG. 4C is a schematic of a horizontal placement of two sway
sensors within the elevator shaft according an embodiment of an
invention;
[0022] FIG. 4D is a schematic of a horizontal placement of one sway
sensor within the elevator shaft according an embodiment of an
invention;
[0023] FIG. 4E is block diagram of a method for horizontal
placement of the sensors within the elevator shaft;
[0024] FIG. 5 is a schematic of one embodiment of the invention
using measurements of at least one sway sensors; and
[0025] FIGS. 6 and 7 are schematic of exemplar embodiments of the
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0026] FIG. 1 shows an example elevator system 100 according to one
embodiment of an invention. The elevator system includes an
elevator car 12 connected by at least one elevator rope to
different components of the elevator system. For example, the
elevator car and a counterweight 14 attached to one another by main
ropes 16-17, and compensating ropes 18. The elevator car 12 can
include a crosshead 30 and a safety plank 33, as known in the art.
A pulley 20 for moving the elevator car 12 and the counterweight 14
through an elevator shaft 22 can be located in a machine room (not
shown) at the top (or bottom) of the elevator shaft 22. The
elevator system can also include a compensating pulley 23. An
elevator shaft 22 includes a front wall 29, a back wall 31, and a
pair of side walls 32.
[0027] The elevator car and the counterweight can have a center of
gravity which is defined as a point at which the summations of the
moments in the x, y, and z directions about that point equal zero.
In other words, the car 12 or counterweight 14 can theoretically be
supported at the point of the center of gravity (x, y, z), and be
balanced, because all of the moments surrounding this point are
cancel out. The main ropes 16-17 typically are attached to the
crosshead 30 of the elevator car 12 at a point where the
coordinates of the center of gravity of the car are projected. The
main ropes 16-17 are similarly attached to the top of the
counterweight 14 at a point where the coordinates of the center of
gravity of the counterweight 14 are projected.
[0028] During the operation of the elevator system, different
components of the system are subjected to internal and external
disturbance, e.g., a force of wind, resulting in lateral motion of
the components. Such lateral motion of the components can result in
a sway of the elevator rope that needs to be measured. Accordingly,
a set of sensors can be arranged in the elevator system to
determine a lateral sway of the elevator rope.
[0029] In various embodiments, different types of sensors can be
arranged in different positions to determine measurements of a
state of the elevator system, such that the sway of the elevator
rope can be properly sensed and/or measured. The actual positions
of the sensors can depend on the type of the sensors used. For
example, the sensors can include a sway sensor 120 configured to
sense a lateral sway of the elevator rope at a sway location
associated with a position of the sway sensor. The sway sensor 120
can be any motion sensor, e.g., a light beam sensor.
[0030] During the operation of the elevator, at least one
measurement of the state of the elevator system is determined and
transmitted 130 to a sway measurement unit 140. The sway
measurement unit determines the sway 150 of the elevator rope by,
e.g., using the measurements and various models of the elevator
system. Various embodiments use different models. For example, some
embodiments use the state model of the elevator system that relates
unknown coefficients of the disturbance to amplitudes of sways of
the elevator rope. Some embodiments also use a system model of the
elevator system that relates amplitude of the disturbance to the
amplitude of the sway. Also, in some embodiments, the state model
is based on an inverse of the system model, as described in more
details below.
[0031] Sway Estimation
[0032] Some embodiments of the invention are based on a realization
that rope sway can be determined based on a model of the elevator
system if the disturbance of the elevator system is known.
Unfortunately, the disturbance of the system is generally unknown
due to, e.g. cost involved in measurement the disturbance. However,
some embodiments are based on another realization that the
disturbance of the system can be determined based on a state model
relating the disturbance of the system to the state of the system
and that state of the system can be determined based on at least
one measurement of the state of the system during the operation of
the system. Examples of types of measurements of the state include
measurement of a sway at various locations of the elevator rope,
measurements of the tension of the elevator rope, and/or
measurements of a vibration of the elevator car.
[0033] FIG. 2 shows an example of a system model 200 of the
elevator system 100. The model 200 is based on parameters of the
elevator systems. Various systems known in the art can be used to
simulate operation of the elevator system according to the model of
the elevator system to simulate an actual sway 212 of the elevator
rope caused by the operation.
[0034] One embodiment performs the modeling based on Newton's
second law. For example, the elevator rope is modeled as a string,
and the elevator car and the counterweight are modeled as rigid
body 230 and 250, respectively. The model of the elevator system is
determined by a partial differential equation according to
.rho. ( .differential. 2 .differential. t 2 + v 2 ( t )
.differential. 2 .differential. y 2 + 2 v ( t ) .differential.
.differential. y .differential. t + a .differential. .differential.
y ) u ( y , t ) - .differential. .differential. y T ( y )
.differential. u ( y , t ) .differential. y + c ( y ) (
.differential. .differential. t + v ( t ) .differential.
.differential. y ) u ( y , t ) = 0 , ( 1 ) ##EQU00001##
wherein
.differential. i .differential. V i ( s ( V ) ) ##EQU00002##
is a derivative of order i of a function s(.) with respect to the
variable V, t is time, y is a vertical coordinate, e.g., in an
inertial frame, u is a lateral displacement of the rope along the x
axes, .rho. is the mass of the rope per unit length, T is the
tension in the elevator rope which changes depending on a type of
the elevator rope, i.e. main rope, compensation rope, c is a
damping coefficient of the elevator rope per unit length, v is the
elevator/rope velocity, .alpha. is the elevator/rope
acceleration.
[0035] Under the two boundary conditions
u(0,t)=f.sub.1(t)
u(l(t),t)=f.sub.2(t), and
f.sub.1(t) is the first boundary condition representing the top
building sway due to external disturbances, e.g. wind conditions,
f.sub.2(t) is the second boundary condition representing the car
sway due to external disturbances, e.g. wind conditions, l(t) is
the length of the elevator rope 17 between the main sheave 112 and
the elevator car 12.
[0036] For example, a tension of the elevator rope can be
determined according to
T=(m.sub.e+.rho.(L(t)-y))(g-.alpha.(t))+0.5m.sub.csg
wherein m.sub.e, m.sub.cs are the mass of the elevator car and the
pulley 240 respectively, and g is the gravity acceleration, i.e.,
g=9.8 m/s.sup.2.
[0037] In one embodiment, the partial differential Equation (1) is
discretized to obtain the model based on ordinary differential
equation (ODE) according to
M{umlaut over (q)}+(C+G){dot over (q)}+(K+H)q=F(t), (2)
wherein q=[q1, . . . , qN] is a Lagrangian coordinate vector, {dot
over (q)}, {umlaut over (q)} are the first and second derivatives
of the Lagrangian coordinate vector with respect to time. N is a
number of vibration modes. The Lagrangian variable vector q defines
the lateral displacement u(y, t) by
u ( y , t ) = j = 1 j = N q j ( t ) .psi. j ( y , t ) + l - y l f 1
( t ) + y l f 2 ( t ) ##EQU00003## .psi. j ( y , t ) = .phi. j (
.xi. ) l ( t ) ##EQU00003.2##
wherein .phi..sub.j(.xi.) is a j.sup.th sway function of the
dimensionless variable .xi.=y/l.
[0038] In Equation (2), M is an inertial matrix, (C+G) constructed
by combining a centrifugal matrix and a Coriolis matrix, (K+H) is a
stiffness matrix and F(t) is a vector of external forces. The
elements of these matrices and vector are given by:
M ij = .rho. .delta. ij ##EQU00004## K ij = 1 4 .rho. l - 2 l . 2
.delta. ij - .rho. l - 2 l . 2 .intg. 0 1 ( 1 - .xi. ) 2 .phi. i '
( .xi. ) .phi. j ' ( .xi. ) .xi. + .rho. l - 1 ( g + l .. ) .intg.
0 1 ( 1 - .xi. ) .phi. i ' ( .xi. ) .phi. j ' ( .xi. ) .xi. + m e l
- 2 ( g + l .. ) .intg. 0 1 .phi. i ' ( .xi. ) .phi. j ' ( .xi. )
.xi. + 1 2 M cs g l - 2 .intg. 0 1 .phi. i ' ( .xi. ) .phi. j ' (
.xi. ) .xi. ##EQU00004.2## H ij = .rho. ( l - 2 l . 2 - l - 1 l ..
) ( 1 2 .delta. ij - .intg. 0 1 ( 1 - .xi. ) .phi. i ( .xi. ) .phi.
j ' ( .xi. ) .xi. ) - c p l . l - 1 ( .intg. 0 1 .phi. i ( .xi. )
.phi. j ' ( .xi. ) .xi. + 0.5 .delta. ij ) ##EQU00004.3## G ij =
.rho. l - 1 l . ( 2 .intg. 0 1 ( 1 - ) .phi. i ( .xi. ) .phi. j ' (
.xi. ) .xi. - .delta. ij ) ##EQU00004.4## C ij = c p .delta. ij
##EQU00004.5## F i ( t ) = - l l ( .rho. s 1 ( t ) + c p s 4 ( t )
) .intg. 0 1 .phi. i ( .xi. ) .xi. .xi. + l ( s 5 ( t ) - .rho. f 1
( 2 ) ( t ) ) .intg. 0 1 .phi. i ( .xi. ) .xi. ##EQU00004.6## s 5 (
t ) = - 2 v .rho. s 2 ( t ) - g ( t ) s 3 ( t ) - c p f 1 ( 2 ) ( t
) ##EQU00004.7## s 1 ( t ) = l l .. - 2 l . 2 l 3 f 1 ( t ) + l . l
2 f . 1 ( t ) + l . l 2 f . 1 ( t ) + 1 l 4 ( l 3 f 2 ( 2 ) ( t ) -
f 2 ( t ) l 2 l ( 2 ) + 2 l l . 2 f 2 ( t ) - 2 l 2 l . f . 2 ( t )
) - f .. 1 ( t ) l ##EQU00004.8## s 2 ( t ) = l . l 2 f 1 ( t ) - f
. 1 l + f . 2 l - f 2 l . l 2 ##EQU00004.9## s 3 ( t ) = f 2 ( t )
- f 1 ( t ) l ##EQU00004.10## s 4 ( t ) = l . l 2 f 1 ( t ) - f . 1
l + f . 2 l . - f 2 l . l 2 ##EQU00004.11## .phi. i ( .xi. ) = 2
sin ( .pi. i .xi. ) , .delta. ij ( kronecker delta )
##EQU00004.12##
wherein {dot over (S)}(.) is a first derivative of a function s
with respect to its variable, the notation s.sup.(2)(.) is a second
derivative of the function s with respect to its variable, and
.intg. v 0 v f s ( v ) v ##EQU00005##
is an integral of the function s with respect to its variable v
over the interval [v.sub.0, v.sub.f]. The Kronecker delta is a
function of two variables, which is 1 if the variables are equal
and 0 otherwise.
[0039] The system models given by Equation (1) and Equation (2) are
two examples of the system models of the elevator system that
relate amplitude of the disturbance to the amplitude of the sway.
Other models based on a different theory, e.g., a beam theory,
instead of a string theory, can be used by the embodiments of the
invention.
[0040] Also, in various embodiments the state model of the system
includes a model of the disturbance of the system having unknown
coefficients. Such formulation allows relating the unknown
coefficients of the disturbance to the measurements of the state.
In some embodiments, such relation is based on an inverse of the
system model described above. For example, in some embodiments, the
disturbance of the elevator system is modeled as a sinusoidal top
sway of the building, which can be modeled by the boundary input
signal f1(t). The boundary input signal can be sinusoidal with
unknown coefficients including one or combination of amplitude,
frequency and phase of the signal. In some embodiments, the
boundary input signal is modeled as a set of sinusoidal signals,
each sinusoidal signal includes its unknown coefficients including
one or combination of amplitude, frequency and phase.
[0041] For example, one embodiment relates a first 262 and a second
264 boundary conditions according to
f 2 ( t ) = f 1 ( t ) sin ( .pi. ( H - y ) 2 H ) , y .di-elect
cons. [ 1 , H ] ##EQU00006##
wherein H is a length of the elevator rope. Then, the system model
is inversed to determine a mapping between the unknown coefficients
of the disturbance to the measurements of the state of the elevator
system, e.g., the amplitudes of the sway. Examples of the mapping
are described below.
[0042] FIG. 3 shows a block diagram of a system and a method 300
for determining a sway of an elevator rope during an operation of
an elevator system. The system and the method can be implemented,
at least in part, using a processor 301. First, a disturbance 315
of the elevator system is determined 310 based on a state model 365
of a state of the elevator system and a number of measurements 370
of the state of the elevator system. In some embodiments, the
number of measurements equals a number of unknown coefficients in
the model of the disturbance.
[0043] For example, if the model of the disturbance includes three
unknown coefficients, e.g., amplitude, frequency and phase of the
sinusoidal signal, then the number of measurements include three
non-zero measurement, e.g., as measured by sensors 375. In some
embodiments, the phase of the sinusoidal signal is not used, and
the number of measurements is reduced to two non-zero measurements.
In another embodiment, the model of disturbance includes multiple
sinusoidal signals, and the number of measurements is adjusted
accordingly. Other variations are possible.
[0044] Next, based on the disturbance 315 and a system model 360 of
the elevator system, the sway of the elevator rope connecting an
elevator car and a pulley is determined 320. In some embodiments,
the sway of the elevator rope includes a sway function 330 of
amplitudes of sways along a length of the elevator rope over time.
As described above, the state model relates the unknown
coefficients of the disturbance to the amplitudes of sways. The
system model relates amplitude of the disturbance to the amplitude
of the sway. Example of the system model includes the model
200.
[0045] In some embodiments, the state model 365 is based on an
inverse 350 of the system model 360. For example, the model of the
elevator system is inverted 350 to determine an estimate of the
building disturbance 315, e.g. wind amplitude and frequency acting
on the top of the building. The building disturbance estimate is
used together with direct system model 360 of the elevator system
to determine an estimate of the elevator rope sway 330. In various
embodiments, the state and the system models are stored in a memory
operatively connected to the processor 301.
[0046] Some embodiments of the invention are also based on a
realization that it can be advantageous to adjust 340 the sway
function based on the measurements of the state of the system. As
discussed above, the measurements of the state can be measured
using various types of the sensors 375. However, one embodiment of
the invention uses sway sensors arranged at the sway location for
measuring the state. This embodiment is advantageous for some
applications, because the measurements of the same sensors can be
used or reused for adjusting the sway.
[0047] FIG. 3B shows an example of such embodiment for adjusting
the sway function. This embodiment compares 380 the measurement 382
of the sway sensors 384 at a time instant and a sway location 383
and estimated sway of the sway function 330 for the same time
instance and the sway location. A graph 395 shows an estimated 392
and an actual 393 sways, and the difference 394 between the sways
392 and 393 at the location 383 and the time instant 385. Hence,
some embodiments shift 390 the sway function 330 based on the
difference 394.
[0048] In various embodiments, the sway sensor is placed in an
elevator shaft of the elevator system, such as the system 100, to
sense a lateral sway of the elevator rope at the sway location. The
arrangement of one or a combination of sway sensors differs among
embodiments. For example, in one embodiment, the sway sensors are
arranged horizontally, i.e. perpendicular to the elevator shaft. In
another embodiment only one sway sensor is used. In another
embodiment, arbitrarily arrangement of the sensor is used. However,
some other embodiments use different type of sensors. For example,
one embodiment uses a set of rope tension sensors is placed along
the rope to sense the rope tension at various locations.
[0049] FIG. 4A shows a placement of the sway sensors in the
elevator shaft according to one embodiment. In this embodiment,
four sway sensors 420 are placed horizontally at the position Ym
430 along the vertical axis [0 Y) 410. The four sway sensors
produce four different sway measurements at four different
instants. These four sway measurements are then used to compute the
system and the state models.
[0050] In this embodiment, four sway measurements can be used as
follows. The first sway measurement is used to initialize the time
reference, i.e. time reference is set to zero when the rope moves
from the vertical sway-free position and the first sway sensor 419
is triggered. Then, the remaining three sway sensors provide three
different sway measurements at three different time instants. These
three measurements are used to determine, using the state model,
the unknown coefficients of the disturbance, i.e. the disturbance
amplitude, the disturbance frequency, and the disturbance phase.
Based on these three coefficients the building disturbance can be
estimated at any time instant. Next, the building disturbances
estimate is used to simulate the elevator system using the system
model to determine the sway elevator rope.
[0051] In the of FIG. 4B, only three sway sensors 421 are used to
determine two coefficients of the disturbance, i.e. amplitude and
frequency. In this embodiment, the value of the phase is
negligible.
[0052] In another embodiment of FIG. 4C, only two sway sensors 429
and 422 are used to determine the coefficients of the building
disturbances. In this embodiment, the first sway sensor 429 is used
to fix the time reference and then the second sensor 422 is used to
collect several sway measurements when the rope crosses the sensor
422 over several time instants. These several sway measurements are
then used to determine several unknown coefficients of the building
disturbances.
[0053] For example, to determine two coefficients of the building
disturbances, two sway measurements of the sensor 422 collected at
two different time instants are used. Similarly, to determine N (N
is positive integer) coefficients of the building disturbances,
e.g. the disturbance is a superposition of many sinusoidal
functions with several amplitudes, frequencies and phases, N sway
measurements of the sensor 422 is used at N different time
instants
[0054] In another embodiment of FIG. 4D, only one sway sensor 423
is sued to determine N sway measurements to estimate N coefficients
of the disturbance.
[0055] In another embodiment of FIG. 4E, N sway sensors 424 are
arranged horizontally at the position Ym 430 in the elevator shaft
to determine N different sway measurements to estimate N
coefficients of the building disturbance.
[0056] FIG. 5 shows a schematic of one embodiment of the invention
using measurements of at least one sway sensors. The at least one
measurement of the state includes amplitudes of the sway of the
elevator rope at the time instant t(i). Then, the disturbance is
determined based on the state model and the amplitudes 510, and the
sway function is determined based on the disturbance and the system
model. The sway function is adjusted at each time the rope crosses
the sway sensor(s) 420.
[0057] For example, the sway of the elevator rope is estimated at
the time instants t(i) according to
u(y,t(i)) 510, for all y.epsilon.[0,l(t(i))] 520,
wherein y is a vertical coordinate 410 in an inertial frame, u is a
lateral displacement of the rope along the x axes, l is the length
of the elevator rope between two boundary locations.
[0058] FIG. 6 shows a schematic of another embodiment that
considers a sinusoidal sway due to external disturbance, which is
modeled based on a first 610 and a second 630 boundary conditions
related by
f 2 ( t ) = f 1 ( t ) sin ( .pi. ( H - y ) 2 H ) , y .di-elect
cons. [ 1 , H ] . ##EQU00007##
[0059] In this embodiment, the system model is used to determine a
relationship 660 F between the unknown coefficients of the
disturbance and the amplitude of the sway. For example in one
embodiment, the system model in equation (2) is considered, where a
sinusoidal disturbance f1(t) of the elevator system is
f.sub.1(t)=A sin(2.pi.ft+.phi.)
wherein A is the amplitude of the disturbance, f is the frequency
of the disturbance, .phi. is the phase of the disturbance, t is
time.
[0060] The sinusoidal disturbance and the relationship relating
f2(t) to f1(t) can be used to formulate lateral sway displacement
equation, e.g.,
u ( y , t ) = j = 1 j = N q j ( t ) .psi. j ( y , t ) + l - y l f 1
( t ) + y l f 2 ( t ) ##EQU00008## .psi. j ( y , t ) = .phi. j (
.xi. ) l ( t ) ##EQU00008.2##
[0061] The relationship between the unknown coefficients of the
disturbance and the amplitude of the sway can be written according
to
F(A,f,.phi.,y,t)=U(y,t),
wherein A is the amplitude of the disturbance, f is the frequency
of the disturbance, .phi. is the phase of the disturbance, y is a
position along the vertical axe [0 Y) of the elevator shaft, t is
time, and U(y, t) is the sway 620. After estimation 670 of the
coefficients of the disturbance is determined (note that we denote
by a the estimate of the variable .alpha.), the estimation of the
boundary input signal f.sub.1(t) and the rope sway for all time
instant noted U(y, t) are determined 680 as well.
[0062] In one embodiment, the sway sensors are located at the
vertical position Y.sub.m 690 in the elevator shaft. The first sway
sensor 640 is placed at the neutral line 695, where the sway
measurement is zero. This sensor is used to detect when the rope
first start swaying and then set a time counter to. After to is set
the second sensor when triggered gives the first non-zero sway
measurement u.sub.1=U(Y.sub.m, t.sub.1) detected at time instant
t.sub.1. Next the third sway sensor when triggered give the second
non-zero sway measurement u.sub.2=U(Y.sub.m, t.sub.2) detected at
time instant t.sub.2. Next the fourth sway sensor when triggered
give the second non-zero sway measurement u.sub.3=U(Y.sub.m,
t.sub.3) detected at time instant t.sub.3.
[0063] After determining three non-zero sway measurement u.sub.1,
u.sub.2 and u.sub.3, the following system of three algebraic
equations with three unknown variables A, f, .phi. can be
solved
a. F(A,f,.phi.,y.sub.m,t.sub.1)=U(Y.sub.m,t.sub.1)=u.sub.1,
b. F(A,f,.phi.,y.sub.m,t.sub.2)=U(Y.sub.m,t.sub.2)=u.sub.2,
c. F(A,f,.phi.,y.sub.m,t.sub.3)=U(Y.sub.m,t.sub.3)=u.sub.3. (3)
[0064] This mapping between the variables A, f, .phi. and the three
rope sway measurements u.sub.1, u.sub.2 and u.sub.3 is inverted 660
to obtain the estimate of the variables A, f, .phi.. The Equation
(3) is solved using for example a Newton-Raphson method to solve
the algebraic nonlinear equations. Next, using the system model
given by, e.g., Equation (2), and the estimate of the coefficients
of the disturbance, an estimate of rope sway U(Y, t), and estimate
of the states q(t), dot(q)(t) for all time instant t and all
vertical position Y along the elevator shaft can be determined.
[0065] FIG. 7 shows a schematic of another embodiment that uses a
number of sensors that is less than a number of measurements of the
state of the system required to determine the disturbance. This
embodiment can be advantageous for applications where the reduction
of the number of sway sensors is beneficial.
[0066] In this embodiment, the sway sensors can be, e.g., arranged
at a vertical position Ym 710 in the elevator shaft. For example,
if two sensors are used, one sensor can be placed at the neutral
line and the other positioned at a distance u.sub.m from the
neutral line. A single sensor positioned at distance from the
neutral line can also be used.
[0067] The sensors are used to determined, e.g., four sway
measurements. For example, if two sensors are used, the first
measurement is obtained when the first sway sensor detects that the
rope moved from the neutral line and this measurement sets the time
reference t.sub.0=0. After we collect the next sway measurement
from the second sway sensor place at u.sub.m this measurement
happens when the second sway sensor is triggered by the rope at the
instant t.sub.1, i.e., U(Y.sub.m,t.sub.1)=u.sub.m. Next, the rope
comes back to trigger the second sensor again at the time instant
t.sub.2, i.e., U(Y.sub.m,t.sub.2)=u.sub.m. Next, the rope can
trigger the second sensor again at the time instant t.sub.3, i.e.,
U(Y.sub.m,t.sub.3)u.sub.m. After necessary number, e.g., three
non-zero sway measurements, is determined, the following system of
algebraic equations can be used to determine three unknown
coefficients A, f, .phi.
a. F(A,f,.phi.,y.sub.m,t.sub.1)=U(Y.sub.m,t.sub.1)=u.sub.m,
b. F(A,f,.phi.,y.sub.m,t.sub.2)=U(Y.sub.m,t.sub.2)=u.sub.m,
c. F(A,f,.phi.,y.sub.m,t.sub.3)=U(Y.sub.m,t.sub.3)u.sub.m. (4)
[0068] This mapping between the coefficients A, f, .phi. and the
three rope sway measurements represented by Equation (4) is
inverted 730 to solve the algebraic system and to determine the
estimate of coefficients of the disturbance 740. Using the elevator
system model given by equation (2) the disturbance, the embodiments
determines an estimate of rope sway U(Y,t) 760, and estimate of the
states q(t), dot(q)(t) 750 for all time instant t and all vertical
position Y along the elevator shaft.
[0069] This embodiment can also adjust the estimated sway to
compensate 770 for errors, e.g., in the phase estimation .phi. and
in the frequency estimation f. To compensate for these errors we
introduce a phase correction step 770. For example, in one
embodiment, the method of phase correction 780 is to record the
time t.sub.2 when the rope sway crosses the second sway sensor
placed at the distance u.sub.m from the neutral line and compare
this time to the time where the rope sway estimation crosses the
same sway value u.sub.m. Then correct the time t.sub.e of the rope
sway function is adjusted 770, e.g., by shifting the sway function
to correct for the phase difference .DELTA. between the rope sway
estimate and the actual rope sway according to
t.sub.e=t.sub.e.DELTA..sub.t, wherein
.DELTA..sub.t=t.sub.2-t.sub.1.
[0070] The above-described embodiments of the present invention can
be implemented in any of numerous ways. For example, the
embodiments may be implemented using hardware, software or a
combination thereof. When implemented in software, the software
code can be executed on any suitable processor or collection of
processors, whether provided in a single computer or distributed
among multiple computers. Such processors may be implemented as
integrated circuits, with one or more processors in an integrated
circuit component. Though, a processor may be implemented using
circuitry in any suitable format.
[0071] Further, it should be appreciated that a computer may be
embodied in any of a number of forms, such as a rack-mounted
computer, a desktop computer, a laptop computer, minicomputer, or a
tablet computer. Also, a computer may have one or more input and
output devices. These devices can be used, among other things, to
present a user interface. Examples of output devices that can be
used to provide a user interface include printers or display
screens for visual presentation of output and speakers or other
sound generating devices for audible presentation of output.
Examples of input devices that can be used for a user interface
include keyboards, and pointing devices, such as mice, touch pads,
and digitizing tablets. As another example, a computer may receive
input information through speech recognition or in other audible
format.
[0072] Such computers may be interconnected by one or more networks
in any suitable form, including as a local area network or a wide
area network, such as an enterprise network or the Internet. Such
networks may be based on any suitable technology and may operate
according to any suitable protocol and may include wireless
networks, wired networks or fiber optic networks.
[0073] Also, the various methods or processes outlined herein may
be coded as software that is executable on one or more processors
that employ any one of a variety of operating systems or platforms.
Additionally, such software may be written using any of a number of
suitable programming languages and/or programming or scripting
tools, and also may be compiled as executable machine language code
or intermediate code that is executed on a framework or virtual
machine. For example, some embodiments of the invention use
MATLAB-SIMULIMK.
[0074] In this respect, the invention may be embodied as a computer
readable storage medium or multiple computer readable media, e.g.,
a computer memory, compact discs (CD), optical discs, digital video
disks (DVD), magnetic tapes, and flash memories. Alternatively or
additionally, the invention may be embodied as a computer readable
medium other than a computer-readable storage medium, such as a
propagating signal.
[0075] The terms "program" or "software" are used herein in a
generic sense to refer to any type of computer code or set of
computer-executable instructions that can be employed to program a
computer or other processor to implement various aspects of the
present invention as discussed above.
[0076] Computer-executable instructions may be in many forms, such
as program modules, executed by one or more computers or other
devices. Generally, program modules include routines, programs,
objects, components, and data structures that perform particular
tasks or implement particular abstract data types. Typically the
functionality of the program modules may be combined or distributed
as desired in various embodiments.
[0077] Also, the embodiments of the invention may be embodied as a
method, of which an example has been provided. The acts performed
as part of the method may be ordered in any suitable way.
Accordingly, embodiments may be constructed in which acts are
performed in an order different than illustrated, which may include
performing some acts simultaneously, even though shown as
sequential acts in illustrative embodiments.
[0078] Use of ordinal terms such as "first," "second," in the
claims to modify a claim element does not by itself connote any
priority, precedence, or order of one claim element over another or
the temporal order in which acts of a method are performed, but are
used merely as labels to distinguish one claim element having a
certain name from another element having a same name (but for use
of the ordinal term) to distinguish the claim elements.
[0079] Although the invention has been described by way of examples
of preferred embodiments, it is to be understood that various other
adaptations and modifications can be made within the spirit and
scope of the invention. Therefore, it is the object of the appended
claims to cover all such variations and modifications as come
within the true spirit and scope of the invention.
* * * * *